It is desirable to employ relatively compact and simple passive components to provide control of resistive loads. For example, variable resistors are often employed to provide some measure of control over heating elements and the like which are typically configured in series with an appropriate voltage source. In this way, the variable resistor effectively functions as a controllable voltage divider.
Certain advantages would be provided by a variable resistor that could compensate for non-linearities inherent in even simple heating element circuits. That is, as both the total current through the resistive heating element as well as the voltage across the heating element are a function of the variable resistance, the relationship between dissipated power in the heating element is related to the position of the variable resistor in a non-trivial manner. This can be unsatisfactory in many applications where the consumer or user has an expectation that the application in which the variable resistor is deployed should have a linear response with respect to the position of the variable resistor (e.g., a slider, dial, knob, or other such user interface mechanically coupled to the variable resistor).
One such application where an improved variable resistor would be advantageous is in the field of vapor-dispensing devices. In general, vapor-dispensing products typically include a volatizable material and a transport system configured to facilitate evaporation of the volatizable material into the surrounding air. For example, in some systems, a liquid is contained in a reservoir bottle; in others, a wax material is used. The housing, which may protrude from a wall outlet (and may thereby supply the voltage source), facilitates the evaporation of the volatizable material into the environment. In such devices, the heating element is thermally coupled to the volatizable material and/or any wicks or other material delivery components. In such a case, it would be desirable for the evaporation rate to be at least partially linear with respect to the position of the variable resistor.